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Practical SSH Port Forwarding Scenarios

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By 千橙工坊
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Practical SSH Port Forwarding Scenarios

SSH port forwarding is a powerful tool for securely tunneling network traffic. Here are three common types—local (-L), remote (-R), and dynamic (-D)—explained with practical use cases.

1. Local Forwarding (-L)

Usage:

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ssh user@remote_host -L 8080:target_host:80

Scenario:

You’re at home and need to access an internal web service (target_host:80) at your workplace. The company server (remote_host) can access it, but you can’t connect directly from home.

How to:

  • Run the above command on your home computer.
  • Visit http://localhost:8080 in your browser. This forwards your request through the SSH tunnel to target_host:80 at your workplace.

How it works:
The SSH client listens on your local port 8080, forwards traffic through the SSH tunnel to remote_host, which then connects to target_host:80.

2. Remote Forwarding (-R)

Usage:

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ssh user@remote_host -R 9090:localhost:3000

Scenario:

You’re developing a web service on your home computer (port 3000) and want colleagues at work to access it via the company server (remote_host).

How to:

  • Run the above command on your home computer.
  • Your colleagues can access http://localhost:9090 on remote_host to reach your local service.

How it works:
The SSH server (remote_host) listens on port 9090 and forwards incoming traffic through the SSH tunnel to your home computer’s port 3000.

3. Dynamic Forwarding (-D)

Usage:

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ssh user@remote_host -D 1080

Scenario:

You want to route all your local traffic through remote_host—for example, to browse the internet securely or bypass restrictions.

How to:

  • Run the above command locally.
  • Set your browser’s SOCKS5 proxy to 127.0.0.1:1080.
  • All browser traffic is tunneled through the SSH connection to remote_host, which then accesses the internet.

How it works:
The SSH client listens on local port 1080, acting as a SOCKS proxy and dynamically forwarding all traffic through the SSH tunnel.

Summary:

  • -L: Local forwarding—access remote internal services from your local machine.
  • -R: Remote forwarding—let remote hosts access services running on your local machine.
  • -D: Dynamic forwarding—route all traffic through a remote host as a proxy.
Tips, CLI
SSH
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